James V. A. Trumbull Louis E. Garrison 1973 <p>A strongly dendritic submarine canyon system with four&nbsp;major canyons occupies a 30-km indentation in the insular shelf off the&nbsp;south coast of Puerto Rico between Guanica and Ponce. &nbsp;Each canyon&nbsp;has several headward branches at depths of 100 to 1,100 m. &nbsp;Each of the&nbsp;five major rivers that reach the coast between Guanica and Ponce is&nbsp;opposite a canyon head, and off each of the rivers a channel 20 to 30 m&nbsp;deep is incised into the insular shelf. &nbsp;The entire canyon system is 40 km&nbsp;long and terminates at a depth of about 3.3 km; no fan or other constructional feature appears to have been formed. &nbsp;A 410-km&nbsp;continuous seismic profiling survey shows that three unconformable stratigraphic units underlie the canyon area. &nbsp;One sample of indurated&nbsp;clay of probable Miocene age was dredged from a canyon-wall outcrop<br />of the middle stratigraphic unit. &nbsp;The three stratigraphic units may be&nbsp;roughly correlative with (in ascending order) the Juana Diaz Formation,<br />the Ponce Limestone, and an unnamed upper section found in a nearby&nbsp;drill hole ashore. &nbsp;Canyon-axis sediment at depths of 700 to 2,200 m is&nbsp;entirely of pelagic origin, indicating that sediment is not now being&nbsp;transported down the canyons.</p> application/pdf en U.S. Geological Survey Geology of a system of submarine canyons south of Puerto Rico article